In scanning microscopy, a sample is illuminated with a light beam in order to observe the reflection or fluorescent light emitted by the sample. The focus of an illumination light beam is moved in an object plane with the help of a controllable beam deflector, generally by tipping two mirrors in an object plane, whereby the axes of deflection are usually positioned perpendicular to each other, so that one mirror deflects in the x-direction and the other in the y-direction. The mirrors are tipped with the help, for example, of galvanometric positioners. The power of the light coming from the object is measured dependent on the position of the scanning beam. Generally, the positioners are provided with sensors to determine the actual position of the mirrors.
In confocal scanning microscopy in particular, an object is scanned in three dimensions with the focus of a light beam.
A confocal scanning microscope generally comprises a light source, a focusing optic with which the light from the source is focused on a pinhole aperture—the so-called excitation aperture—, a beam splitter, a beam deflector to control the beam, a microscope optic, a detection aperture, and detectors to detect the detection or fluorescent light. The illumination light is coupled via a beam splitter. The fluorescent or reflection light coming from the object returns to the beam splitter via the beam deflector, passes through it, and finally focuses on the detection aperture, behind which are the detectors. Detection light that does not originate directly from the focal region takes another light path and does not pass through the detection aperture, so that pixel information is obtained that leads to a three-dimensional image as a result of sequential scanning of the object. In most cases, a three-dimensional image is achieved by layered data imaging, whereby the path of the scanning light beam ideally describes a meander pattern on or in the object. (Scanning a line in the x-direction at a constant y-position, then interrupting x-scanning and y-repositioning to the next line to be scanned, and then scanning this line at a constant y-position in negative x-direction, etc.). To enable layered data imaging, the sample table or the objective is repositioned after scanning a layer so that the next layer to be scanned is brought into the focal plane of the objective.
When analyzing biological samples with a so-called FRAP (fluorescence recovery after photobleaching), the temporal recovery behavior of a sample region after a bleaching process is analyzed. A scanning microscope is known from DE 102 33 549 A1 which may, among other things, be used for FRAP analysis. The scanning microscope has a light source that emits an illumination light beam for illuminating a sample. The illumination light beam passes along an illumination beam path and can be guided over or through a sample, as the case may be, by a beam deflector. A further light source that emits a manipulation light beam is provided, which passes along the manipulation beam path. Both the manipulation light beam and the illumination light beam are guided over or through the sample, as the case may be, by the beam deflector.
A laser scanning microscope with at least two light sources and two beam deflectors is known from U.S. Pat. No. 6,094,300. Each of the light sources is assigned to a beam deflector. The laser light beams emitted by the light sources can scan the sample independently of each other with both of the beam deflectors.
A method for scanning a region of interest of a sample is known from U.S. Pat. No. 2002/0196535 A1, whereby different scan lines are scanned under various conditions of illumination.